Add chopped onions to milk in saucepan and bring to a boil; remove from heat and set aside to steep. Pour milk over bread crumbs and allow bread to soak. Chop asparagus into ½ ‘’ pieces and simmer in boiling water until bright green. Melt butter in skillet, and cook mushrooms until tender, add salt and pepper, and set aside. Break eggs and beat until smooth, add herbs and plenty of salt and pepper, add bread crumbs with remaining milk, asparagus, and mushrooms with their juices, and 2/3 or the cheese. Mix thoroughly and pour into a greased 8 by 12 inch baking dish; sprinkle remaining cheese on top and bake at 350 degrees for about 45 minutes until puffy and golden.